This invention relates to liquid cooled electric generating apparatus and more particularly, to the liquid circulation system therein and methods for filling that liquid circulation system.
Liquid cooled electric generating apparatus such as that used in aircraft electric power systems, may include an oil cooled generator or a generator-converter integrated package. A liquid circulation system used in such apparatus typically includes a primary reservoir for containing coolant oil and a pump driven by the generator rotor which circulates the coolant oil through numerous passages in the generator stator and an associated heat exchanger. Coolant oil is also delivered to a generator rotor and associated bearings.
When the apparatus is installed on an aircraft engine or a drive pad, it must be charged with coolant oil to a proper level. If the oil is introduced directly into the reservoir, the oil passages around the stator, all oil lines leading to and from the heat exchanger, and the heat exchanger internal passages will not be filled with oil. These lines and passages will be filled when the generator's pump is operated, but this will lower the level in the reservoir and require a second filling. Alternatively, if oil is introduced into the stator passageway, thereby filling the stator, heat exchanger, reservoir and associated passages, oil will also fill the rotor cavity. When the generator is spun, the spinning rotor will clear the rotor cavity, thereby increasing the amount of oil in the reservoir and requiring that the reservoir be drained to achieve the proper oil level.
Both oil filling scenarios described above are undesirable and time consuming. This invention seeks to overcome the deficiencies in the above filling scenarios such that the proper coolant level can be achieved in a single filling operation.